1. Field of the Invention
This invention relates to sir welding systems. More specifically, the invention is a thermal stir welding system employing ultrasonic energy to assist in the welding process.
2. Description of the Related Art
Stir welding is a form of welding that utilizes a small stir pin to mix abutting or faying surfaces of two pieces of material (e.g., metal materials) to thereby form a joint between the two pieces of material. There are several types of stir welding systems/processes. For example, thermal stir welding (TSW) is a solid-state welding process capable of joining metallic alloys without melting. In this process, weld work pieces to be joined are heated and drawn by heavy forces between two containment plates applying compressive forces to the work pieces. The TSW stir pin is located between the containment plates and is rotated to create a join between the weld work pieces as they are drawn through the containment plates. The TSW process can be improved by reducing the friction forces between the weld work pieces and the containment plates. While a lubricant (e.g., oil, synthetic lubricant, etc.) could be used to reduce the friction forces, the lubricant contaminates the weld resulting in weld defects.